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Full text of "Text Book Of Mechanical Engineering"

1:,

1     I

11

Examples.

Remarks.—In cooling, the rivet exerts great grip on the
plate, giving frictional strength to the joint, but caulking
diminishes this, so it is not allowed for. Rivets over 6" long
.would break in cooling, so must be hammered up cold.

The formula for boiler strength, j)tons r—jt 17, can now be used
to better advantage, Construct.a table shewing t and?; tinder
all conditions, and after finding t x 77 from the formula, choose
such values of each as will meet the case when multiplied. Such
a table precedes this page, where the pitch has been taken at its
theoretical value; but must" be decreased to secure staunchness
where necessary, as with the thinner plates in the last column.
The efficiency table is not from practical tests ^ but jrom p, 4.07
fcrmulcB.

Example 14.—A steel Lancashire boiler 8 ft. dia. is loaded with
. i oo Ibs. per square inch. Find ^, and indicate the joint yon would
' use.

p^r-At*   .: , „ = IOOX4^2 =-357
2240 x 6        JJ'

i. Single riveted lap joint         t
	rj = 2 x -49 = -367 4

2. Single riveted butt joint     )
	9

3. Double riveted lap joint    \
	,= T?x-69=-382

4. Double riveted butt joint      /
	„= Li «3 =.363

Something between (3) and (4) would have to be adopted ; say
(4) with -J" plate and spacing like (3) for staunchness.

Example 1 5. — Two lengths of mild steel tie rod 7"xi"are to be
connected with double butt straps. Determine dimensions and
efficiency. (Hons, Mach, Constr. Exam., 1893.)

^=1*3.   Centre to edge =1*5 xi -25 = 1*87 5
vu" for one'rivet, in double shear = 2 x 1*09=2*18

7-1-3 = 57 width of pierced plate :
Checking we have :
Strength of rivets = 2 x

. • .         =3 rivets say,

^ X5 x 3^



Strength of pierced plate = (7 - 1 -3) x i x 6 =34*2 tons